Method for striping conductor coatings



Feb. 5, 1963 G. c. RoLLlNs ErAL 3,076,235

METHOD Foa STRIPING commc'rcm` commes Filed March 9, 1960 2 Sheets-Sheet1 ATTORNEY Feb. 5, 1963 G. c. RoLLlNs Erm. 3,076,235

METHOD Fon STRIPING coNDucToR commes 2 Sheets-Sheet 2 Filed March 9,1960 INVENTORS GORDON 6. ROLL/NS WAL TER L. ROBERTS BY /54 ATTORNEY3,076,235 METHOD FR STRliilNG CONDUCTR CA'lllNGS Gordon C. Rollins andWalter L. Roberts, Hickory, N., assignors to Superior Cable Corporation,Hickory, N.,

a corporation of North Carolina Filed Mar. 9, 19ml, Ser. No. 13,8%Claims. (Cl. iig-59) This invention relates to the striping of theinsulating coating of wire conductors and cables and consists moreparticularly in new and useful improvements in a method for applying anidentifying stripe to a wire coating of polyethylene or the like, bybonding to said coating at the time of the extrusion process, a separatefilament of similar or compatible material.

In the manufacture of cables used in the communications iield forexample, the cable is usually composed of a series of insulatedconductors and because of the large number of similar conductorscontained within a single cable, it is necessary to identify individualconductors or groups of conductors embodied in the cable.Conventionally, two basic methods of conductor striping have been used,namely the ink striping method and the method wherein two or moreextruders are utilized, each containing plastic materials of the desiredcolor.

ln the ink striping method, a stripe of colored ink is lapplied to thewire by means of a wheel ruiming in an ink bath and transferring the inkto the surface of the wire coating against which the wheel is pressed,the passage of the wire causing the wheel to turn. An alternate inkstriping method employs a hypodermic needle which rests against thesurface of the running wire and ink is forced through the hypodermicneedle onto the coating.

The ink striping method has presented several diiicult problems, bothduring manufacture and during use of the end product. The ink must havea precisely controlled viscosity to enable it to be carried by theprinting wheel to the wire coating and to enable it to be transferred tothe wire coating in a sharp, delineated stripe. lf the ink is too thin,it will run on the surface of the Wire, making an uneven blurred stripe.lf it is too thick, the wheel will transfer an excess amount of ink andit will smear on the surface of the wire. The viscosity is controlled bythe addition of a thinner to the ink solution and depends entirely onthe operators ability to judge the amount of thinner required.

After the ink is on the wire, it must be dried before it can be takenover a sheave or wound on a reel. This is done by passing the wirethrough a heated tube and the speed at which the ink can be drieddetermines the production rate and usually restricts high speedprocessing. ln the case of a hypodermic needle applicator, the viscosityand homogeneity of the ink is even more critical since the needle is soeasily clogged.

Perhaps the most diicult problem with ink striping is obtaining -a bondbetween the ink and the plastic coating on the wire. With polyvinylchloride insulation, a reasonably good bond can be obtained, but withpolyethylene insulation which is now largely in use, it is impossible toobtain a good bond. A poor bond between the ink stripe and theinsulation results in aking of the ink from the insulation duringfurther processing of the wire and in handling the wire in the field..Flaking of the inl: or loss of the ink on the surface due to abrasionresults in loss of ability to identify a wire by its colored tate latent@free 3,076,235 Patented Feb. 5, 1953 ductor coating, it is impossibleto put enough red pigment in an ink to completely mask the blackcoloring under the ink. The result, of course, is a stripe with a washedout appearance which can result in erroneous identification of the wire.

The other method of striping which utilizes the two or more extruderscontaining different colored plastic materials, involves apparatuswherein the eXtruders force the plastic materials through a common oricethrough which the wire is running, forming an insulating coating on thewire. The colors of this coating correspond to the colors in each of theextruders. The most serious objection to this type of striping is thefact that color changes require the disassembly and cleaning out of oneor more of the eXtruders which is a time consuming operation.

lt is therefore the primary object of the present invention to overcomethe above-noted difficulties and to provide a method for applying apreformed monofilament to an extruded wire coating, the material of saidmonolament being similar to or compatible with that of the plasticcoating on the wire and wherein the stripe is pressed into the still hotplastic coating on the wire at a point irnmediately posterior to theextruder die orifice.

Another object of the invention is to provide a method of this characterwherein a monofilament stripe is applied to the wire coating while thelatter is still hot, whereby, since the material of the monoiilament andthe plastic wire covering are similar, the material in the monotllamentsoftens and forms a very effective heat sealed bond to the plastic wirecovering.

A further object of the invention is to provide a method lfor applying amonofilarnent stripe to a wire coating with a heat sealed bond tothereby avoid flaking and, since the monolament is embedded deeply inthe insulation, any abrasion great enough to remove the monolamentstripe would completely destroy the insulation.

Still another object of the invention is to provide a method of thischaracter wherein no solvents or thinners are required and bondingoccurs so quickly that no practical limit of processing speed exists andthe thickness of the monolilament permits sharp, clear contrast betweenthe stripe co-lor and the background color of the Wire coating.

A marked advantage of the present invention resides in the fact that themonollament need not be completely embedded in the conductor insulation,but can be permitted to protrude above the surface of the insulation,creating in effect a raised ridge along the surface of the conductorinsulation, thus enabling the stripe to be felt as well as seen for usein identifying striped conductors from plain conductors.

A still further object of the invention is to provide a method forapplying a monolament stripe to a wire coating wherein the stripecolors, when applied to a common background color, can be changedwithout stopping the process, resulting in an obvious saving in time andscrap material.

With the above and other objects in View which will appear as thedescription proceeds, the invention consists in the novel featuresherein set forth, illustrated in the accompanying drawings, and moreparticularly pointed out in the appended claims.

Referring to the drawings in which numerals of like character designatesimilar parts throughout the several views:

FlG. l is a diagrammatic view illustrating the apparatus of theinvention in side elevation;

FIG. 2 is an enlarged detail of the striping device in side elevation;

HG. 3 is an edge view of the striping device shown in FlG. 2;

FIG. 4 is Ian enlarged transverse sectional view of a coated wire withan embedded stripe; and

FIG. 5 is Ia similar view showing a raised stripe or rib.

In the drawings, referring first to FIG. l, 6 represents a conventionalWire payoff reel from which conductor wire 7 is fed through a suitableelectric preheater or the like 8, to the extruder die 9 of aconventional extruding device 10. The material for providing theinsulating coating for the wire 7, preferably polyethylene, is fed inheated condition, to the extrusion die 9 from reservoir 11, and as thewire passes through the orifice of the extruder die 9, it is coated4with polyethylene in the usual manner. Y

As the coated wire leaves the extiuder orifice 9 and while it is stillhot, a preformed monofilament 12 of polyethylene `is applied to thecoating by means of a striping roller 13, said monofilament being fedfrom a payoff reel 14 carried by a 4suitable support 15. The filament12, while preferably of polyethylene, may be of other compatiblematerial and of any desired color.

Turning to FIGS. 2 and 3 which illustrate the striping device more indetail, the roller 13 is rotatably supported -by a bifurcated yoke 16suspended from a threaded stem 17 which is vertically adjustable in acomplementary threaded opening in a holding bracket 18 supportedposterior to the extruder 9. The threaded stem 17 extends through thebracket 18 and, fixed to its upper end, is an adjusting knob 19 wherebythe position of the roller 13 with respect to the coated Wire 7 may beadjusted and the pressure of the peripheral engagement of the rollerwith the wire may be controlled. A knurled lock nut 20 is preferablyprovided for maintaining aselected vertical position of the roller 13.

Preferably the periphery of the roller 13 is grooved as at 21 to embracethe coated wire 7 immediately after it leaves the orifice of theextruder 9 and in order to present the filament 12 in the center of thewire, a supplemental groove 22 is provided at the base of the maingroove 21. As best seen in FIGURES 2 and 3, the groove 21 is of a widthand depth to substantially centrally receive the strand of filament 12and simultaneously directly engage the peripheral coating 7a of the wire7, on either side of the filament. Thus, as the hot coated wire 7advances from the extruder, its frictional engagement with the peripheryof the freely rotating roller 13 causes the latter to rotate,simultaneously advancing the monofilament 1'2 of a selected color andpressing the same into periphery of the wire coating. As the material inthe monofilament 12 is similar to that of the plastic wire covering .andas the latter is still hot, the material in the m'onolament softens andforms an effective heat sealed bond to the plastic wire covering.

Returning n-ow to FIG. l, after the monofilament 12 is applied to thecoating of wire 7, the striped wire ad' vances through a conventionalcooling trough 23 and after beingv cooled passes to a capstan andtake-up for storage.

As before indicated, the identifying monofilament stripe may becompletely embedded in the plastic coating of the wire, or it may bepermitted to protrude above the surface of the insulation in the form ofa raised ridge. In' FIG. 4, We have shown the monofilament 12 completelyembedded and lying flush with the surface of the :insulating coating 7a,while in FIG. 5, the mono-filament 12 is only partly embedded in theinsulation 7a, so as to form a raised ridge on the surface of the coatedwire.

The extent to which the monofilament 12 is embedded in the coating 7a isdetermined by the pressure applied by the roller 13 which, as beforeindicated, is adjustable iby means of the knob 19 'and its threaded stem17. Also, the depth of the supplemental groove 22 in the roller 13 willhave a certain effect upon the depth of embedding the monofilament inthe insulating coating. In fact, in some instances it may be desirableto eliminate this supplemental groove where it is desired to completelyembed the mono-filament.`

The preformed monofilament 12 may be an extruded filament `of thedesired material or it may consist of an elongated strip slit lfrom asheet of plastic material. In either event, the filament is fed inpreformed condition in the manner above described.

In this connection, it might be noted that while the convention-alextruded stripe method possesses certain of the advantages of themonofilament stripe of the present invention, it would be extremelydifiicult to produce a raised ridge effect which is made possible in thepresent instance by the application of the preformed monofil-ament andthe pressure control of its application to the hot wire coating.

From the foregoing, it is believed that the invention may be readilyunderstood by those 4skilled in the art without further description, itbeing borne in mind that numerous changes may be made in the detailsdisclosed without departing from the spirit of the invention as setforth in the following claims.

We claim:

l. A method of striping extruded wire coatings, comprismg advancing anot plastic coated wire longitudinally from an extruding die,continuously and independently of said die, applying longitudinally tothe periphery of the hot plastic coating of said wire as the latteradvances, a length of completely preformed, unheated, thread-likestriping filament of plastic material compatible With said coating,simultaneously embedding said filament at least partially beneath thesurface of said hot coating while confining the line of contact of sai-dfilament to a pathy lying within the lateral limits of said coated Wire,and cooling the striped, coated wire.

2. A method of striping the plastic coating of a wire being extrudedhot, from an extruding die, comprising embedding an end of a completelypreformed, unheated, thread-like striping filament, of plastic materialcompatible with said coating, in the periphery of said coating as thelatter adavncesrin heated condition from said extruding die,longitudinally advancing said coated wire and filament while confiningthe line of Contact of said filament to a path lying within the laterallimits of said coated wire and simultaneously embedding said filamentlongitudinally at least partially beneath the surface of said coating,and cooling the striped, coated wire.

3. A method as claimed in claim 2, including progres- .sively applyingpressure to said filament to embed the latter in said coating as thewire and filament are adx vanced.

4. A method as claimed in claim 2, wherein said striping filament is ofthe same material as that of said coating. 5. A method as claimed inclaim 2, including controlling the depth of embedding of said filamentby applying a regulated lateral pressure' thereon as the wire advances.

References Cited in the tile of this patent UNITED STATES PATENTS575,888 Hin Jim. 26, 1897 815,571 Williams Mar. 20, 1906 FOREIGN PATENTS684,196 Great Britain Dec. 10, 1952 690,508 Great Britain Apr. 22, 1953

1. A METHOD OF STRIPING EXTRUDED WIRE COATINGS, COMPRISING ADVANCING AHOT PLASTIC COATED WIRE LONGITUDINALLY FROM AN EXTRUDING DIE,CONTINUOUSLY AND INDEPENDENTLY OF SAID DIE, APPLYING LONGITUDINALLY TOTHE PERIPHERY OF THE HOT PLASTIC COATING OF SAID WIRE AS THE LATTERADVANCES, A LENGTH FILAMENT OF PLASTIC MATERIAL COMPATIBLE WITH SAIDCOATING, FILAMENT OF PLASTIC MATERIAL COMPATIBLE WITH SAID COATING,SIMULTANEOUSLY EMBEDDING SAID FILAMENT AT LEAST PARTIALLY BEENEATH THESURFACE OF SAID HOT COATING WHILE CONFININF THE LINE OF CONTACT OF SAIDFILAMENT TO A PATH LYING WITHIN THE LATERAL LIMITS OF SAID COATED WIRE,AND COOLING THE STRIPED, COATED WIRE.